Kinematics of Cenozoic Shortening of the Hotan Anticline along the Northwestern Margin of the Tibetan Plateau (western Kunlun, China)

Kinematic constraints on the Cenozoic deformation along the northwestern edge of the Tibetan Plateau remain limited. Combining surface geological data and seismic profiles, we document the structural geometry and kinematics of the large-scale east-west striking Hotan anticline, along the foothills of the Western Kunlun Range. Four new balanced cross sections are constructed, and the temporal evolution of deformation is deciphered from the exceptionally well-imaged growth strata at the front of the fold. This anticline results from a broad fault-bend fold, subsequently deformed by a footwall duplex. The total shortening across the whole structure is relatively constant along strike, from similar to 40 to similar to 35 km. However, the shortening accommodated by the duplex varies laterally from similar to 50-40% to 0% of the total shortening. Two distinct successive patterns of growth strata are recognized and are interpreted to be representative of deformation on the ramp anticline, followed by deformation on the duplex. The onset of deformation initiated by similar to 16 Ma. Deformation of the underlying duplex began at similar to 12 Ma to the west and subsequently propagated eastward. From these results, we determine a shortening rate of similar to 5 mm/yr from similar to 16 to similar to 8-9 Ma across the Hotan thrust system, followed by a significant decrease in shortening rate, possibly down to <0.5 mm/yr. We explore the significance of this deceleration of deformation at the scale of the Western Kunlun foothills and at a broader regional scale as it may point to a regional kinematic reorganization by the late Miocene.